1. Field of the Invention
The present invention relates to a screen rake which is used to clean a screen disposed in a water channel such as a sewage channel, which screen rake is movable from a rest position above the water level in the channel to a position where the comb portion thereof is in engagement with the bottom of the screen, then moved such that the comb portion is moved along the vertically oriented screen bars, then along a generally horizontal path to a point above a collecting tank where the contents of the comb portion are dumped, and then moved back to the initial rest position. The invention also relates to a screen rake which is pivotable around a horizontal axis; wherein the attached comb portion is pivotable with respect to the rake arm around a horizontal axis; wherein the rake arm is swivelable by means of a driving mechanism and movable in a vertical plane; wherein the driving mechanism includes an endless chain means which is pivotally connected to the rake arm and which is driven around fixedly mounted rotatable sprocket wheels and caused to move along a guide track; wherein the end of the rake arm opposite the end to which the comb portion is attached via a pivot means having a horizontal pivot axis to one end of an elongated support means; and wherein the elongated support means is also attached via a pivot means to a fixed supporting structure, the latter pivot means having a horizontal pivot axis.
2. Summary of the Prior Art
As shown in U.S. Pat. No. 4,107,040, an apparatus of the type herein contemplated is known wherein the rake arm is fabricated as a twin-arm assembly comprising two spaced apart individual arms, and wherein a special revolving chain is provided for each of the two arms, each endless chain moving along its own respective guide track.
Apart from the high costs of such a double guidance system, due to the need for the use of transverse struts, the construction of the apparatus is quite cumbersome, especially the welding together of the various interrelated parts. In addition, it is difficult to arrange the parallel parts in precise alignment, especially the spaced apart guide tracks. Thus cants are produced which lead to vibration and/or oscillation of the rake arm during movement. As a result, the bearings, the chains and the guide tracks are placed under great stress, and this leads to abrasion of the parts and ultimately malfunctions. In addition, as a result of the vibration and/or oscillation of the twin-armed rake, and most particularly the uncontrollable lateral movements thereof, the successful engagement of the teeth of the comb means attached thereto in between the vertically oriented bars of the screen will be jeopardized, which of course defeats the operational functioning of the entire device.
It is an object of the present invention to provide an apparatus of the general type mentioned for cleaning screens located in water channels, but which apparatus is simple to assemble, will not encounter operational difficulties known heretofore, and which will not be costly to produce.